EP0317581B1 - High-speed milling or drilling heads - Google Patents

Abstract

PCT No. PCT/EP88/00358 Sec. 371 Date Mar. 6, 1989 Sec. 102(e) Date Mar. 6, 1989 PCT Filed Apr. 28, 1988 PCT Pub. No. WO88/08767 PCT Pub. Date Nov. 17, 1988.High speed milling or drilling tool of the type including a rotatable head which carries several circumferentially arranged cutting insert holders for reversible cutting inserts retained by dogs. Each insert has a pair of parallel top surfaces bounded by four orthogonal end surfaces, two of which are received against perpendicular sidewalls in an open pocket of the holder. Each top surface has at least one pair of elongate clamping indentations which are formed as surfaces of rotation and lie at a like angle beta to the adjacent end surface of the insert.

Description

The invention relates to a milling or drilling head equipped with cutting plates (11), according to the preambles of claims 1 and 2.

Milling or drilling heads are increasingly being fitted with ceramic indexable inserts in order to fully exploit the high cutting speeds that these inserts enable. The high cutting speeds in conjunction with a specific cutting edge design result in surfaces that are hardly inferior to ground surfaces, so that one work step can be saved by machining with ceramic cutting plates, to a limited extent also with hard metal cutting plates.

Due to the high speeds and the resulting high peripheral speeds, high demands are placed on the clamping elements, since the centrifugal forces that occur ensure that the insert is no longer securely seated in the clamping element. In disc milling cutters, therefore, as is known from DE-GM 85 03 545, hole inserts of the usual type have been used, which have a through hole in the surface center of their secondary free surface, which is provided with a countersink, engage in the clamping elements and exert pressure against the contact surfaces of the Bring out the seat on the disc body. Apart from the fact that the required stability is not given, in particular at high speeds and when approaching the workpiece, these hole inserts tend to crack to an increased extent. DE-GM 85 27 924 therefore proposes to insert a clamping trough into a cutting insert on one side, the clamping trough having a trapezoidal shape in its longitudinal section, a triangular shape in its cross section, or being arranged as a frustoconical depression. This clamping trough is also arranged in the secondary surface, which has the required size. The depth of the clamping trough corresponds essentially to half the thickness of the insert.

In contrast to face milling cutters, side milling cutters have a completely different requirement profile, because the forces on the side milling cutters attack completely differently and are also uneven. With each revolution of the side milling cutter, a tooth of the side milling cutter "strikes" onto the workpiece to be machined and removes a chip, the subsequent tooth then performs the same process. So it is a constant hitting, which leads to a rattling, which can be adjusted the insert. With disc milling cutters, it is therefore absolutely necessary to press the cutting plate, which is arranged radially to the direction of rotation in slots in the disk, against the side wall of the slot, which is generally done by means of clamping wedges.

Roll milling cutters are to be classified in the same category as side milling cutters, since, as DE-A 25 49 757 shows, they consist of side milling cutters arranged side by side on a shaft.

The disc recesses arranged in it serve to accommodate an indexable insert and a clamping body. The indexable insert can be designed as a perforated insert and is secured in this case by a grub screw which engages in the central hole of the clamping plate, but recesses can also be made in the cover surfaces of the indexable insert, in the projections of the clamping wedge or the disc recess intervention. The recess in the top surfaces of the indexable insert has the shape of a circular section, the secant of which runs parallel to the axis of rotation of the milling cutter. The circular segment-shaped recess runs at an angle equal to / less than 15 degrees to the top surface. With this configuration, a very high pressure is exerted on the wedge clamp Side wall reached. System errors of the cutting plate can not be corrected by tightening the wedge element, it is not ensured that the plate is drawn into the plate seat to the bottom, since the main force component is directed against the side wall of the recess.

With this construction, the cutting forces counteract the centrifugal force. The clamping wedge is therefore attacked in the region of the depression which is adjacent to the cutting edge. It is not possible to adjust such an insert because it does not have a separate holder that can be adjusted in the milling head.

For milling heads that are designed for planning and drilling heads that are designed for spindle-out, there are completely different requirements compared to the side milling cutters. That is, that the cutting plates have secondary free areas, the dimensions of which are not sufficient for clamping and into which troughs for receiving clamping elements cannot be introduced without the risk of damage to cutting edges.

The present invention is therefore based on the prior art according to DE-A 2549757 the task of providing fastenings of the cutting plates in the case of fast-rotating milling or drilling heads, in particular those which work with a peripheral speed of over 250 m / s, which ensures that that the inserts remain in the specified position even during the work cycle, when clamping by the applied clamping forces up to the rear stop in the Pull the holder in, furthermore not be damaged or destroyed by thermal influences.

This object is achieved in a generic tool by the characterizing features of claim 1 and claim 2.

Both possible solutions have in common that recesses which have a specific geometric shape of part of a rotating body are introduced into the top surfaces of the cutting plates. The invention makes use of the phenomenon of self-locking in order to keep the insert in the prescribed position. In addition, a certain angle configuration ensures that the insert is inevitably pulled to the stop when the clamping claw is tightened and in this position even at high peripheral speeds remains.

The subclaims describe preferred embodiments of the invention.

• Fig. 1 zeigt in perspektivischer Darstellung einen Fräskopf,
• Fig. 2 als Draufsicht im Ausschnitt ein Spannelement dieses Fräskopfes,
• Fig. 3 die Draufsicht auf ein unter einem Winkel δ angeordnetes Spannelement,
• Fig. 4 in vergrößerter Darstellung die Seitenansicht
  einer Schneidplatte im Halter,
• Fig. 5 die Draufsicht auf den Halter gemäß Fig. 4,
• Fig. 6 die Seitenansicht der Schneidplatte gemäß Fig 5 im Schnitt mit angedeutetem Rotationskörper,
• Fig. 7 die Draufsicht auf die Schneidplatte gemäß Fig. 6,
• Fig. 8 die Seitenansicht einer Schneidplatte im Schnitt mit dargestelltem Rotationskörper,
• Fig. 9 die Draufsicht auf die Schneidplatte gemäß Fig. 8,
• Fig. 10 die Seitenansicht eines Halters nebest Spannpratze für Schneidplatten gemäß Fig. 9,
• Fig. 11 eine weitere Schneidplattenform mit entsprechend dargestelltem Rotationskörper in der Seitenansicht im Schnitt und
• Fig. 12 eine Draufsicht auf eine Schneidplatte gemäß Fig. 11.

The invention is explained below with reference to the drawings.

• 1 shows a perspective view of a milling head,
• 2 a top view of a clamping element of this milling head,
• 3 shows the top view of a clamping element arranged at an angle δ,
• Fig. 4 is an enlarged side view
  a cutting plate in the holder,
• 5 shows the top view of the holder according to FIG. 4,
• 6 shows the side view of the cutting insert according to FIG. 5 in section with the rotation body indicated,
• 7 is a top view of the insert according to FIG. 6,
• 8 is a side view of a cutting insert in section with the rotating body shown,
• 9 is a top view of the insert according to FIG. 8,
• 10 shows the side view of a holder along with clamping claw for cutting inserts according to FIG. 9,
• 11 shows a further insert shape with a correspondingly illustrated rotating body in a side view in section and
• 12 is a plan view of a cutting insert according to FIG. 11.

The milling head consists of a carrier body (16) which has grooves (17) in which the holders (6), which hold the cutting plate (11), are mounted via retaining screws (30). The holders (6) can be positioned using adjusting screws (19). The clamping claw (9) is fastened to the holder (6) by means of a clamping screw (20), it engages with its nose (21) in a clamping recess (1) of the cutting plate (11) and pulls the cutting plate when the clamping screw (20) is tightened (11) to the right system (22) and the left system (23). The cutting plate (11) is essentially aligned.

The clamping troughs (1), as the figures show, are arranged in the cover surfaces (2) of the cutting plate (11) and have the shape of a section of a lateral surface (7, 7 ', 7˝, 7˝') of a rotating body on. According to FIG. 6, the rotating body rotating about the axis of rotation (10) is a cylinder (33) through which a curved surface (3) and a flat surface in the form of a circular section (4) is formed. The secant (5) of the circular section (4) runs at an angle (β) to the adjacent peripheral surface (24), which is between 13 and 32 degrees, and at an angle (90 degrees - ε), where (ε) is the angle between the direction of movement (X) and the peripheral surface (24) adjacent to it. In Figure 23, an angle of 16 degrees is shown.

The circular section (4) of the clamping trough (1) is inclined at an angle α of 15 to 45 degrees with respect to the top surface (2). The size of the angle Δ, which the envious surfaces, that is to say the top surface (2) and the circular section (4), form with one another, is between 135 and 165 degrees. In Figure 8, this angle Δ is shown as an angle of 150 degrees.

In the case of the embodiment according to FIG. 8, the lateral surface (7 ') of the clamping trough (1) is part of an ellipsoid (34), which is created by rotating the ellipse (15) about an axis of rotation (10), which is at an angle γ to the top surface ( 2) the cutting plate (11) is inclined. The ellipse axis (14) is inclined by the angle (µ) with respect to the axis of rotation (10), resulting in the angle (α 7T) at the trough (1 '). The longitudinal axis (8 ') of the corresponding trough (1') therefore has the shape of a flat arc piece, one Connection line through the intersection of the arc with the top surface (2) of the cutting plate (11) at the same angle β as the secant (5) of the circular section (4) described in Figures 6 and 7. For the sake of simplicity, however, it was assumed in the application that this arc, that is to say the longitudinal axis (8) of the clamping trough (1), is a straight line which runs at the angle β.

4 to 12, the cutting plate (11) is provided with a circumferential chamfer (12) which forms the transition from the top surfaces (2) to the peripheral surfaces (24). Two of these circumferential surfaces (24) rest on the systems (22) and (23), the tiling only taking place in the upper third and in the direction of the support (25) there is a free space (26) which ensures that the cutting plate (11) rests without beaks on the support (25) which forms the base of the recess (27) in the adjustable holder (6).

Figure 10, which shows a cutting plate according to Figures 8 and 9, shows that between the nose (21 ') of the clamping claw (9) and the lateral surface (7') of the rotating body which forms the clamping trough (1 ') , there is a point contact. By tightening the clamping screw (20), the clamping claw (9) is moved downwards, whereby it is pressed with its rear end (41) onto the chamfer (40) on the holder (6), which causes it to be moved backwards and thereby the cutting insert (11) with the peripheral surface (24) to the system (23).

A further version of the clamping trough design is shown in FIGS. 11 and 12, where the rotating body, the lateral surface (7˝ ') of which forms the clamping trough (1˝), consists of a cylinder (35) with a hemispherical head (36) attached, the center point ( P₃) is moved in a plane parallel to the top surface (2) of the cutting plate (11). A part of the cylinder (F) enters under the top surface (2) of the cutting plate (11˝), so that in this area of the clamping trough (1˝) a slope is formed at an angle (α˝).

Claims (8)

1. A milling head or drilling head provided with cutting plates (11), in which the cutting plates (11) in two parallel covering surfaces (2) have at least one clamping trough (1) each, which trough is defined by a flat surface, which extends at an angle α to the covering surface (2) and is engaged by a clamping member, and by a curved surface (3) forming with the flat surface a segment of a circle (4), characterized by the combination of the following features:
the cutting plates (11) consist of sintered ceramics,
the clamping member is constructed as a clamping claw,
the segment of a circle (4) of the clamping trough (1) is inclined at an angle α of 15 to 45 degrees to the covering surface (2),
the clamping trough (1) has a depth T of 1.2 to 3.8 mm,
the cutting plate (11) is so gripped in a support (6) arranged in the milling or drilling head that the edge (5) of the segment of a circle (4) extends at an angle β to the adjacent
circumferential surface (24) of the cutting plate and at an angle of 90 degrees less ε to the direction of adjustment (X) of the adjustable support (6).

2. A milling head or drilling head provided with cutting plates (11), in which the cutting plates (11) in two parallel covering surfaces (2) have at least one clamping trough (1) each, which have the hollow form of a portion of a body of revolution, wherein a clamping member engages the clamping trough, characterized by the combination of the following features:
the cutting plate (11) consists of sintered ceramics and the clamping member is constructed as a clamping claw,
the clamping trough has a depth T of 1.2 to 3.8 mm,
the axis (10) of the body of revolution forming the peripheral surface (7) of the clamping trough (1) is inclined at an angle γ of 15 to 45 degrees to the covering surface (2),
the cutting plate (11) is so gripped in a support (6) adjustably mounted in the milling or drilling head that the longitudinal axis (8) of the clamping trough (1) extends at an angle β of 13 to 32 degrees to the adjacent circumferential surface (24) and at an angle of 90 degrees minus ε to the direction of adjustment (X) of the adjustable support (6).

3. A milling head or drilling head according to claim 2, characterized in that the body of revolution is a ellipsoid (34).

4. A milling head or drilling head according to claim 2, characterized in that the body of revolution is a cylinder (35) with a himispherical end part (36).

5. A milling head or drilling head according to claim 3, characterized in that the long axis (10) of the body of revolution of the ellipse (15) forming the peripheral surface (7) of the clamping trough (1) is inclined at an angle γ of 15 to 45 degrees of the covering surface (2).

6. A milling head or drilling head according to claim 1, charcterized in that the segment of a circle has a radius R_k which is 0.2 to 0.5 times an inscribed circle limited by the cutting edges of the cutting plate (11).

7. A milling head or drilling head according to one of claims 3 and 5, characterized in that the radius R of the ellipse (15), which forms the ellipsoid (14), is 1.2 to 2.5 times and the radius r of the ellipse (15) is 0.25 to 0.5 times an inscribed circle limited by the cutting edges of the cutting plate (11).

8. A milling head or drilling head according to claim 4, characterized in that the cylinder diameter is 0.8 to 1.5 times an inscribed circle limited by the cutting edges of the cutting plate (11).

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